The present invention relates to the general field of optical fiber accessories and is particularly concerned with an optical fiber winding tool.
The use of optical fibers for telecommunication systems and other applications has become increasingly prevalent over the past few years. As is well known in the art, optical fibers are typically hair thin structures, capable of transmitting light signals at high rates and with low signal loss. They are ideally suited to the high requirements of digital transmission and, hence, are well matched to the evolving worldwide transmission network.
The most popular medium for light wave transmission through optical fibers is glass, a solid whose structure is amorphous. Commercial optical fibers are drawn from a pre-form, an elongated cylinder of glass having an inner core and an outer cladding, with the thickness of the core and the cladding typically being in the same ratio in the fiber as they are in the pre-form. During the drawing process, the pre-form is fed into a heated region where it necks down to the fiber size as the fiber is pulled from the heat zone. A coating is applied to the freshly drawn fiber before it touches any capstans or rollers. The coating protects the fiber from the environment and cushions it from external forces that induce micro-bending losses. The drawn fiber is taken up on spools in such a manner that the end portions of the fiber on each spool are available for testing. The spools of drawn, tested fibers are subsequently used to supply ribbon and cabling processes and apparatus.
The winding parameters during take up must be carefully controlled. Collection of the fiber at low tension is necessary in order to minimize damage to the fiber or coating thereon and to reduce the effect of micro-bending and macro-bending losses on the transmission media. The winding tension is minimized and the distribution of fiber across a spool is controlled to provide a desired package profile and to facilitate unwinding at a subsequent operation. Hence, great care is usually taken in order to minimize potential damages to the fiber during the initial winding step following the drawing of the fiber. Unfortunately, such concern with the possible damages resulting from improper handling of optical fibers, particularly during the critical winding steps, is often neglected once the fiber leaves the fiber-manufacturing site.
The specific handling requirements of optical fibers are directly linked to their inherent structure. Indeed, optical fibers being made of glass are characterized by their brittleness. A typical glass fiber will stretch elastically to about 7% strain and break abruptly without undergoing any permanent deformation. The actual breaking strengths between fibers will vary widely and depend on a variety of factors. The reason for this wide range is attributed to submicroscopic cracks in the fiber surface. These cracks can be inherent to the glass itself or a result of manufacturing processes and handling of the fiber.
The mere manipulation of the fiber, even by a skilled worker, may potentially lead to reduce mechanical and/or optical properties. Indeed, localized pressure on the fiber tends to deform the core, which is a softer glass than the cladding, causing radiated losses and mode coupling also referred to as micro-bending losses. Micro-bends consist of microscopic random deviations of a fiber around its straight nominal position. The amplitude of the deviation is typically a few microns or less and their period less than a millimeter. In multi-mode fibers, micro-bends cause light to be exchanged among the various guided modes, some of which have higher losses than others. In both multi-mode and single mode fibers, light can couple into modes that escape from the core. The small deflections usually result from fiber coating, cabling, packaging or other localized forces. They can also be created during the manual handling of the fiber by squeezing the fiber between the fingers of the intended user. Although micro-bending losses typically return to zero when the localized forces are removed, they may potentially create permanent losses.
Fibers exposed to active environments and under stress, weaken with time because existing cracks grow. Termed static fatigue, this crack-growth phenomenon limits the residual stress that a fiber can sustain over a period of time and imposes a minimum bend radius on fibers. Indeed, bending a fiber produces tensile stresses along its outer portion and compressive stresses along its inner portion. The minimum bend radius depends on various factors including specifications in given applications. For most applications, a 1xe2x80x3 minimum bend radius is usually recommended as being a comfortable minimum bend radius for an installed fiber, both to minimize bending induced loss and also to preserve fiber lifetime. A minimum bend radius also needs to be respected during winding operations. This tends to be difficult, especially with relatively short strips of optical fibers.
Hence, aside from breakage, optical fiber communication performance may be degraded by micro-cracks or micro-bends in the fiber generated by bending or other stresses imposed on the fiber. Such damage to an optical fiber not only reduces the fibers long-term durability, but it also causes losses in optical signal strength and content. As mentioned previously, great care is usually taken during initial handling and winding of the fibers at the manufacturing site. In order to reduce the risks of physically damaging the fiber, the control of fiber tension during initial winding immediately after the drawing of the fiber requires relatively sophisticated equipment.
In order to control fiber tension in the freshly drawn fiber, the latter is typically allowed to form a catenary between the capstan and the take up. As the spool fills, the catenary tends to decrease in length and it becomes necessary to decrease take up motor speed under controlled conditions. This is typically accomplished with an electro-optical system including a closed circuit television camera, which detects any change in the height of the fiber catenary and causes changes in the take up motor speed. Once initially wound, the fiber is shipped on a spool to other companies or clients that either use the fiber or further process the latter.
There exists a plurality of situations wherein an optical fiber needs to be re-wound into a coil after the initial winding on a spool at the manufacturing site. Some applications, such as the manufacturing of optic sensing devices, inherently require winding of the fiber. Other situations are related to general handling of the fiber. For example, it may be desirable to mount optical devices, such as multiplexers, demultiplexers, switches or the like, on relatively short strips of fibers, commonly referred to as xe2x80x9cpigtailsxe2x80x9d that are eventually spliced to longer segments of optical fiber. The mounting of such optical components on strips of optical fiber requires handling and temporary storage of the fiber segments. The use of relatively sophisticated equipment and method conventionally used for initially winding the drawn fiber as herein above disclosed is not well suited to this type of application.
In assembly lines wherein optical components are attached to strips of optical fiber, the latter is wound at various stations. For example, once the optical component is attached to a pigtail, the pigtail is typically manually wound into a coil prior to shipment to an intended customer. The manual winding of pigtails presents numerous drawbacks. The operation is both tedious and time consuming. Furthermore, it involves repetitive and relatively unergonomical movements that may potentially lead to work related injuries such as tendonitis or the like.
Furthermore, as mentioned previously, manual winding of the pigtails may potentially lead to damages in the fiber with resulting loss of efficiency and reduced longevity. Accordingly, there exists a need for an optical fiber winding device.
Advantages of the present invention include that the proposed optical fiber winding tool allows for the winding of a strip of optical fiber into a generally toroidal-shaped coil with low residual strain. Also, the proposed optical fiber winding tool reduces the risks of inducing mechanical stresses to the fiber during the winding operation, thereby reducing the risk of mechanically damaging the fiber and/or reducing its optical performance by micro-bending losses or other phenomena. Furthermore, the proposed optical fiber winding tool allows for winding strips of optical fiber while preserving a predetermined minimum bend radius throughout the winding process.
Still further, the proposed optical fiber winding tool allows for the winding of strips of optical fiber having optical or mechanical components attached thereto. The proposed optical fiber winding tool also allows for the winding of cables having a wide range of mechanical properties. Furthermore, the proposed optical fiber winding tool allows for the winding of both relatively short and relatively long strips of optical fibers in various contexts.
Still further, the proposed optical fiber winding tool allows for the winding of strips of optical fiber through a set of relatively easy and ergonomic steps, thus reducing both mental and physical fatigue. Furthermore, the proposed optical fiber winding tool allows for the winding of optical cables without requiring special tooling or manual dexterity. The proposed optical fiber winding tool is designed so as to be compact and easily carried with minimal effort to diverse locations so that it can be used in various settings with reduced risks of damaging the optical fiber winding tool or strips of fiber inserted therein.
Furthermore, the proposed optical fiber winding tool is designed so as to be manufacturable using conventional forms of manufacturing and conventional materials so as to provide an optical fiber winding tool that will be economically feasible, long lasting and relatively trouble free in operation. The proposed optical fiber winding tool is designed so as to be relatively mechanically simple so as to provide a durable winding tool requiring relatively low maintenance.
Optionally, the proposed optical fiber winding tool only requires the installation of a segment of a strip of optical fiber within the tool, the winding operation being performed automatically without requiring manual intervention. Furthermore, the proposed optical fiber winding tool optionally allows for the simultaneous winding of more than one strip of optical fiber into a single coil.
In accordance with an embodiment of the invention, there is provided an optical fiber winding tool for winding a strip of optical fiber into a coil, the optical fiber winding tool being mountable on a generally flat supporting surface and allowing manual winding of the strip of optical fiber by the hands of an intended user, the strip of optical fiber defining a strip first longitudinal end, an opposed strip second longitudinal end and a strip intermediate section extending therebetween, the optical fiber winding tool comprising:a guiding body having a body outer surface and defining a guiding recess, the guiding recess defining a recess peripheral edge delimiting a recess aperture leading into the guiding recess, the recess aperture being in an aperture geometrical plane; a recess peripheral wall having a recess peripheral surface that extends inwardly into the guiding body from the recess peripheral edge, the recess peripheral surface delimiting the boundary of the guiding recess; a fiber inlet aperture formed in the guiding body and leading into the guiding recess, the fiber inlet aperture being sized for allowing the slidable insertion of the strip of optical fiber into the guiding recess; the recess is peripheral wall being configured and sized such that when the recess aperture is mounted over the supporting surface and the strip of optical fiber is inserted through the fiber inlet aperture, the strip first longitudinal end contacts the supporting surface and the recess peripheral surface abuttingly guides the strip intermediate section so that further insertion of the strip of optical fiber into the guiding recess causes the strip of optical fiber to wind into a coil against the recess peripheral surface adjacent the supporting surface.
Preferably, the guiding recess is configured and sized such that the strip of optical fiber maintains a predetermined minimal bend radius as it abuttingly contacts the recess peripheral surface during the winding of the strip of optical fiber into a coil. Conveniently, the recess peripheral surface has a generally frustro-conical configuration defining a recess apex region. Also, conveniently, the fiber inlet aperture is positioned adjacent the recess apex region.
Preferably, the guiding body also defines an alignment section having a guiding channel that extends from the body outer surface to the fiber inlet aperture, the guiding channel being configured and sized so that the strip of optical fiber maintains a predetermined minimal bend radius as it slides therethrough. Typically, the guiding body includes a removable body segment allowing selective lateral access to the interior of the guiding recess.
Conveniently, the optical fiber winding tool further comprises a fiber outlet slot formed in the guiding body for allowing an outlet segment of the optical fiber segment to extend out of the guiding recess in a direction substantially parallel to the aperture geometrical plane and tangential relative to the coil.
Preferably, the optical fiber winding tool further comprises a hand guiding means attached to the guiding body for guiding the hands of the intended user as the intended user drives the strip of optical fiber into the guiding recess. Conveniently, the optical fiber winding also further comprises a multiple fiber separating means mounted on the guiding body for physically separating and guiding at least two individual optical fiber strips when the at least two individual optical fiber strips are inserted simultaneously into the guiding recess through the inlet aperture.
Preferably, the fiber separating means includes a separating block mounted on the guiding body, the separating block having at least two separating slots formed therein for individually receiving one of the at least two individual optical fiber strips.
Preferably, the optical fiber winding tool further comprises a driving means attached to the guiding body for driving the strip of optical fiber into the guiding recess through the fiber inlet aperture. Typically, the driving means includes a fluid guiding means for guiding the flow of a pressurized fluid in such a manner that the pressurized fluid is in contact with the strip of optical fiber and drives the strip of optical fiber through the fiber inlet aperture and into the guiding recess.
Preferably, the driving means includes a driving head attached to the guiding body, the driving head defining a driving head external surface and having a main fluid channel extending therethrough, the main fluid channel defining a main channel longitudinal axis, the main fluid channel being configured and sized for slidably receiving the strip of optical fiber and for allowing through flow of the pressurized fluid therealong, the driving head also including a fluid connecting means for allowing the main fluid channel to be connected to a source of pressurized fluid.
Conveniently, the driving head is provided with a head panel, the head panel being movable between a panel open configuration and a panel closed configuration, wherein when the head panel is in the panel open configuration the head panel allows access to the main fluid channel from a direction oriented at an angle relative to the main channel longitudinal axis and when the head panel is in the closed configuration the head panel prevents access to the main fluid channel from a direction at an angle relative to the main channel longitudinal axis.
Preferably, the driving means includes an auxiliary channel extending from the driving head external surface to the main fluid channel at angle relative thereto, the auxiliary channel being in fluid communication with the main fluid channel; the auxiliary channel being provided with a fluid coupling means for coupling the auxiliary channel to a source of pressurized gas.